11、Mybatis之逆向工程

11.1、正向与逆向工程概述

• 正向工程：先创建Java实体类，由框架负责根据实体类生成数据库表；例如Hibernate是支持正向工程的。

• 逆向工程：先创建数据库表，由框架负责根据数据库表，反向生成Java实体类、mapper接口和映射文件。

11.2、环境搭建

11.2.1、创建新module

创建名为mybatis_mbg的新module，过程参考5.1节

11.2.2、添加打包方式和依赖及插件

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.rain</groupId>
    <artifactId>mybatis_mbg</artifactId>
    <version>1.0-SNAPSHOT</version>
    <!--打包方式-->
    <packaging>jar</packaging>

    <!--依赖-->
    <dependencies>
        <!-- Mybatis核心 -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.7</version>
        </dependency>
        <!-- junit测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <!-- MySQL驱动 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <!-- log4j日志 -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
    </dependencies>

    <build>
        <!-- 构建过程中用到的插件 -->
        <plugins>
            <!-- 具体插件，逆向工程的操作是以构建过程中插件形式出现的 -->
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.0</version>
                <!-- 插件的依赖 -->
                <dependencies>
                    <!-- 逆向工程的核心依赖 -->
                    <dependency>
                        <groupId>org.mybatis.generator</groupId>
                        <artifactId>mybatis-generator-core</artifactId>
                        <version>1.3.2</version>
                    </dependency>
                    <!-- MySQL驱动 -->
                    <dependency>
                        <groupId>mysql</groupId>
                        <artifactId>mysql-connector-java</artifactId>
                        <version>5.1.49</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>

</project>

11.3、创建逆向工程的配置文件

注意：文件名必须是generatorConfig.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
    <!--
    targetRuntime属性: 设置执行生成逆向工程的版本
        MyBatis3Simple: 生成基本的CRUD（简洁版）
        MyBatis3: 生成带条件的CRUD（进阶版）
    -->
    <context id="DB2Tables" targetRuntime="MyBatis3Simple">
        <!-- 数据库的连接信息 -->
        <jdbcConnection driverClass="com.mysql.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/ssm?characterEncoding=utf-8"
                        userId="root"
                        password="root">
        </jdbcConnection>
        <!-- javaBean的生成策略-->
        <javaModelGenerator targetPackage="org.rain.mybatis.pojo" targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
            <property name="trimStrings" value="true" />
        </javaModelGenerator>
        <!-- SQL映射文件的生成策略 -->
        <sqlMapGenerator targetPackage="org.rain.mybatis.mapper" targetProject=".\src\main\resources">
            <property name="enableSubPackages" value="true" />
        </sqlMapGenerator>
        <!-- Mapper接口的生成策略 -->
        <javaClientGenerator type="XMLMAPPER" targetPackage="org.rain.mybatis.mapper" targetProject=".\src\main\java">
            <property name="enableSubPackages" value="true" />
        </javaClientGenerator>
        <!-- 逆向分析的表 -->
        <!-- tableName设置为*号，可以对应所有表，此时不写domainObjectName -->
        <!-- domainObjectName属性指定生成出来的实体类的类名 -->
        <table tableName="t_emp" domainObjectName="Emp"/>
        <table tableName="t_dept" domainObjectName="Dept"/>
    </context>
</generatorConfiguration>

11.4、执行mybatis-generator插件

• 找到mybatis-generator插件，并双击执行

11.5、插件执行效果(简洁版)

11.5.1、总体概览

注意：如图所示，实体类、接口和映射文件都自动生成了

11.5.2、实体类生成内容示例

package org.rain.mybatis.pojo;

public class Dept {
    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column t_dept.dept_id
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    private Integer deptId;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column t_dept.dept_name
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    private String deptName;

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column t_dept.dept_id
     *
     * @return the value of t_dept.dept_id
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    public Integer getDeptId() {
        return deptId;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column t_dept.dept_id
     *
     * @param deptId the value for t_dept.dept_id
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    public void setDeptId(Integer deptId) {
        this.deptId = deptId;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column t_dept.dept_name
     *
     * @return the value of t_dept.dept_name
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    public String getDeptName() {
        return deptName;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column t_dept.dept_name
     *
     * @param deptName the value for t_dept.dept_name
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    public void setDeptName(String deptName) {
        this.deptName = deptName == null ? null : deptName.trim();
    }
}

11.5.3、mapper接口生成内容示例

package org.rain.mybatis.mapper;

import java.util.List;
import org.rain.mybatis.pojo.Dept;

public interface DeptMapper {
    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    int deleteByPrimaryKey(Integer deptId);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    int insert(Dept record);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    Dept selectByPrimaryKey(Integer deptId);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    List<Dept> selectAll();

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Wed Jul 05 11:25:17 CST 2023
     */
    int updateByPrimaryKey(Dept record);
}

11.5.4、映射文件生成内容示例

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="org.rain.mybatis.mapper.DeptMapper" >
  <resultMap id="BaseResultMap" type="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Wed Jul 05 11:25:17 CST 2023.
    -->
    <id column="dept_id" property="deptId" jdbcType="INTEGER" />
    <result column="dept_name" property="deptName" jdbcType="VARCHAR" />
  </resultMap>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Wed Jul 05 11:25:17 CST 2023.
    -->
    delete from t_dept
    where dept_id = #{deptId,jdbcType=INTEGER}
  </delete>
  <insert id="insert" parameterType="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Wed Jul 05 11:25:17 CST 2023.
    -->
    insert into t_dept (dept_id, dept_name)
    values (#{deptId,jdbcType=INTEGER}, #{deptName,jdbcType=VARCHAR})
  </insert>
  <update id="updateByPrimaryKey" parameterType="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Wed Jul 05 11:25:17 CST 2023.
    -->
    update t_dept
    set dept_name = #{deptName,jdbcType=VARCHAR}
    where dept_id = #{deptId,jdbcType=INTEGER}
  </update>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Wed Jul 05 11:25:17 CST 2023.
    -->
    select dept_id, dept_name
    from t_dept
    where dept_id = #{deptId,jdbcType=INTEGER}
  </select>
  <select id="selectAll" resultMap="BaseResultMap" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Wed Jul 05 11:25:17 CST 2023.
    -->
    select dept_id, dept_name
    from t_dept
  </select>
</mapper>

11.6、进阶版逆向工程

11.6.1、修改逆向工程配置文件

11.6.2、删除之前简单版生成的内容

++++++++++++++++++++分割线++++++++++++++++++++++

11.6.3、执行mybatis-generator插件

11.6.4、插件执行效果(进阶版)

11.6.4.1、总体概览

注意：进阶版生成的实体类，比简洁版的多了xxxExample

11.6.4.2、实体类生成内容示例

package org.rain.mybatis.pojo;

public class Dept {
    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column t_dept.dept_id
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    private Integer deptId;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database column t_dept.dept_name
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    private String deptName;

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column t_dept.dept_id
     *
     * @return the value of t_dept.dept_id
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public Integer getDeptId() {
        return deptId;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column t_dept.dept_id
     *
     * @param deptId the value for t_dept.dept_id
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public void setDeptId(Integer deptId) {
        this.deptId = deptId;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method returns the value of the database column t_dept.dept_name
     *
     * @return the value of t_dept.dept_name
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public String getDeptName() {
        return deptName;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method sets the value of the database column t_dept.dept_name
     *
     * @param deptName the value for t_dept.dept_name
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public void setDeptName(String deptName) {
        this.deptName = deptName == null ? null : deptName.trim();
    }
}

11.6.4.3、实体类Example生成内容示例

package org.rain.mybatis.pojo;

import java.util.ArrayList;
import java.util.List;

public class DeptExample {
    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    protected String orderByClause;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    protected boolean distinct;

    /**
     * This field was generated by MyBatis Generator.
     * This field corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    protected List<Criteria> oredCriteria;

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public DeptExample() {
        oredCriteria = new ArrayList<Criteria>();
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public void setOrderByClause(String orderByClause) {
        this.orderByClause = orderByClause;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public String getOrderByClause() {
        return orderByClause;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public void setDistinct(boolean distinct) {
        this.distinct = distinct;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public boolean isDistinct() {
        return distinct;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public List<Criteria> getOredCriteria() {
        return oredCriteria;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public void or(Criteria criteria) {
        oredCriteria.add(criteria);
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public Criteria or() {
        Criteria criteria = createCriteriaInternal();
        oredCriteria.add(criteria);
        return criteria;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public Criteria createCriteria() {
        Criteria criteria = createCriteriaInternal();
        if (oredCriteria.size() == 0) {
            oredCriteria.add(criteria);
        }
        return criteria;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    protected Criteria createCriteriaInternal() {
        Criteria criteria = new Criteria();
        return criteria;
    }

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public void clear() {
        oredCriteria.clear();
        orderByClause = null;
        distinct = false;
    }

    /**
     * This class was generated by MyBatis Generator.
     * This class corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    protected abstract static class GeneratedCriteria {
        protected List<Criterion> criteria;

        protected GeneratedCriteria() {
            super();
            criteria = new ArrayList<Criterion>();
        }

        public boolean isValid() {
            return criteria.size() > 0;
        }

        public List<Criterion> getAllCriteria() {
            return criteria;
        }

        public List<Criterion> getCriteria() {
            return criteria;
        }

        protected void addCriterion(String condition) {
            if (condition == null) {
                throw new RuntimeException("Value for condition cannot be null");
            }
            criteria.add(new Criterion(condition));
        }

        protected void addCriterion(String condition, Object value, String property) {
            if (value == null) {
                throw new RuntimeException("Value for " + property + " cannot be null");
            }
            criteria.add(new Criterion(condition, value));
        }

        protected void addCriterion(String condition, Object value1, Object value2, String property) {
            if (value1 == null || value2 == null) {
                throw new RuntimeException("Between values for " + property + " cannot be null");
            }
            criteria.add(new Criterion(condition, value1, value2));
        }

        public Criteria andDeptIdIsNull() {
            addCriterion("dept_id is null");
            return (Criteria) this;
        }

        public Criteria andDeptIdIsNotNull() {
            addCriterion("dept_id is not null");
            return (Criteria) this;
        }

        public Criteria andDeptIdEqualTo(Integer value) {
            addCriterion("dept_id =", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdNotEqualTo(Integer value) {
            addCriterion("dept_id <>", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdGreaterThan(Integer value) {
            addCriterion("dept_id >", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdGreaterThanOrEqualTo(Integer value) {
            addCriterion("dept_id >=", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdLessThan(Integer value) {
            addCriterion("dept_id <", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdLessThanOrEqualTo(Integer value) {
            addCriterion("dept_id <=", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdIn(List<Integer> values) {
            addCriterion("dept_id in", values, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdNotIn(List<Integer> values) {
            addCriterion("dept_id not in", values, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdBetween(Integer value1, Integer value2) {
            addCriterion("dept_id between", value1, value2, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdNotBetween(Integer value1, Integer value2) {
            addCriterion("dept_id not between", value1, value2, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptNameIsNull() {
            addCriterion("dept_name is null");
            return (Criteria) this;
        }

        public Criteria andDeptNameIsNotNull() {
            addCriterion("dept_name is not null");
            return (Criteria) this;
        }

        public Criteria andDeptNameEqualTo(String value) {
            addCriterion("dept_name =", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameNotEqualTo(String value) {
            addCriterion("dept_name <>", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameGreaterThan(String value) {
            addCriterion("dept_name >", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameGreaterThanOrEqualTo(String value) {
            addCriterion("dept_name >=", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameLessThan(String value) {
            addCriterion("dept_name <", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameLessThanOrEqualTo(String value) {
            addCriterion("dept_name <=", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameLike(String value) {
            addCriterion("dept_name like", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameNotLike(String value) {
            addCriterion("dept_name not like", value, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameIn(List<String> values) {
            addCriterion("dept_name in", values, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameNotIn(List<String> values) {
            addCriterion("dept_name not in", values, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameBetween(String value1, String value2) {
            addCriterion("dept_name between", value1, value2, "deptName");
            return (Criteria) this;
        }

        public Criteria andDeptNameNotBetween(String value1, String value2) {
            addCriterion("dept_name not between", value1, value2, "deptName");
            return (Criteria) this;
        }
    }

    /**
     * This class was generated by MyBatis Generator.
     * This class corresponds to the database table t_dept
     *
     * @mbggenerated do_not_delete_during_merge Thu Jul 06 11:01:56 CST 2023
     */
    public static class Criteria extends GeneratedCriteria {

        protected Criteria() {
            super();
        }
    }

    /**
     * This class was generated by MyBatis Generator.
     * This class corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    public static class Criterion {
        private String condition;

        private Object value;

        private Object secondValue;

        private boolean noValue;

        private boolean singleValue;

        private boolean betweenValue;

        private boolean listValue;

        private String typeHandler;

        public String getCondition() {
            return condition;
        }

        public Object getValue() {
            return value;
        }

        public Object getSecondValue() {
            return secondValue;
        }

        public boolean isNoValue() {
            return noValue;
        }

        public boolean isSingleValue() {
            return singleValue;
        }

        public boolean isBetweenValue() {
            return betweenValue;
        }

        public boolean isListValue() {
            return listValue;
        }

        public String getTypeHandler() {
            return typeHandler;
        }

        protected Criterion(String condition) {
            super();
            this.condition = condition;
            this.typeHandler = null;
            this.noValue = true;
        }

        protected Criterion(String condition, Object value, String typeHandler) {
            super();
            this.condition = condition;
            this.value = value;
            this.typeHandler = typeHandler;
            if (value instanceof List<?>) {
                this.listValue = true;
            } else {
                this.singleValue = true;
            }
        }

        protected Criterion(String condition, Object value) {
            this(condition, value, null);
        }

        protected Criterion(String condition, Object value, Object secondValue, String typeHandler) {
            super();
            this.condition = condition;
            this.value = value;
            this.secondValue = secondValue;
            this.typeHandler = typeHandler;
            this.betweenValue = true;
        }

        protected Criterion(String condition, Object value, Object secondValue) {
            this(condition, value, secondValue, null);
        }
    }
}

11.6.4.4、mapper接口生成内容示例

package org.rain.mybatis.mapper;

import java.util.List;
import org.apache.ibatis.annotations.Param;
import org.rain.mybatis.pojo.Dept;
import org.rain.mybatis.pojo.DeptExample;

public interface DeptMapper {
    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int countByExample(DeptExample example);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int deleteByExample(DeptExample example);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int deleteByPrimaryKey(Integer deptId);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int insert(Dept record);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int insertSelective(Dept record);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    List<Dept> selectByExample(DeptExample example);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    Dept selectByPrimaryKey(Integer deptId);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int updateByExampleSelective(@Param("record") Dept record, @Param("example") DeptExample example);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int updateByExample(@Param("record") Dept record, @Param("example") DeptExample example);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int updateByPrimaryKeySelective(Dept record);

    /**
     * This method was generated by MyBatis Generator.
     * This method corresponds to the database table t_dept
     *
     * @mbggenerated Thu Jul 06 11:01:56 CST 2023
     */
    int updateByPrimaryKey(Dept record);
}

11.6.4.5、映射文件生成内容示例

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="org.rain.mybatis.mapper.DeptMapper" >
  <resultMap id="BaseResultMap" type="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    <id column="dept_id" property="deptId" jdbcType="INTEGER" />
    <result column="dept_name" property="deptName" jdbcType="VARCHAR" />
  </resultMap>
  <sql id="Example_Where_Clause" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    <where >
      <foreach collection="oredCriteria" item="criteria" separator="or" >
        <if test="criteria.valid" >
          <trim prefix="(" suffix=")" prefixOverrides="and" >
            <foreach collection="criteria.criteria" item="criterion" >
              <choose >
                <when test="criterion.noValue" >
                  and ${criterion.condition}
                </when>
                <when test="criterion.singleValue" >
                  and ${criterion.condition} #{criterion.value}
                </when>
                <when test="criterion.betweenValue" >
                  and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}
                </when>
                <when test="criterion.listValue" >
                  and ${criterion.condition}
                  <foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >
                    #{listItem}
                  </foreach>
                </when>
              </choose>
            </foreach>
          </trim>
        </if>
      </foreach>
    </where>
  </sql>
  <sql id="Update_By_Example_Where_Clause" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    <where >
      <foreach collection="example.oredCriteria" item="criteria" separator="or" >
        <if test="criteria.valid" >
          <trim prefix="(" suffix=")" prefixOverrides="and" >
            <foreach collection="criteria.criteria" item="criterion" >
              <choose >
                <when test="criterion.noValue" >
                  and ${criterion.condition}
                </when>
                <when test="criterion.singleValue" >
                  and ${criterion.condition} #{criterion.value}
                </when>
                <when test="criterion.betweenValue" >
                  and ${criterion.condition} #{criterion.value} and #{criterion.secondValue}
                </when>
                <when test="criterion.listValue" >
                  and ${criterion.condition}
                  <foreach collection="criterion.value" item="listItem" open="(" close=")" separator="," >
                    #{listItem}
                  </foreach>
                </when>
              </choose>
            </foreach>
          </trim>
        </if>
      </foreach>
    </where>
  </sql>
  <sql id="Base_Column_List" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    dept_id, dept_name
  </sql>
  <select id="selectByExample" resultMap="BaseResultMap" parameterType="org.rain.mybatis.pojo.DeptExample" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    select
    <if test="distinct" >
      distinct
    </if>
    <include refid="Base_Column_List" />
    from t_dept
    <if test="_parameter != null" >
      <include refid="Example_Where_Clause" />
    </if>
    <if test="orderByClause != null" >
      order by ${orderByClause}
    </if>
  </select>
  <select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Integer" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    select
    <include refid="Base_Column_List" />
    from t_dept
    where dept_id = #{deptId,jdbcType=INTEGER}
  </select>
  <delete id="deleteByPrimaryKey" parameterType="java.lang.Integer" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    delete from t_dept
    where dept_id = #{deptId,jdbcType=INTEGER}
  </delete>
  <delete id="deleteByExample" parameterType="org.rain.mybatis.pojo.DeptExample" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    delete from t_dept
    <if test="_parameter != null" >
      <include refid="Example_Where_Clause" />
    </if>
  </delete>
  <insert id="insert" parameterType="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    insert into t_dept (dept_id, dept_name)
    values (#{deptId,jdbcType=INTEGER}, #{deptName,jdbcType=VARCHAR})
  </insert>
  <insert id="insertSelective" parameterType="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    insert into t_dept
    <trim prefix="(" suffix=")" suffixOverrides="," >
      <if test="deptId != null" >
        dept_id,
      </if>
      <if test="deptName != null" >
        dept_name,
      </if>
    </trim>
    <trim prefix="values (" suffix=")" suffixOverrides="," >
      <if test="deptId != null" >
        #{deptId,jdbcType=INTEGER},
      </if>
      <if test="deptName != null" >
        #{deptName,jdbcType=VARCHAR},
      </if>
    </trim>
  </insert>
  <select id="countByExample" parameterType="org.rain.mybatis.pojo.DeptExample" resultType="java.lang.Integer" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    select count(*) from t_dept
    <if test="_parameter != null" >
      <include refid="Example_Where_Clause" />
    </if>
  </select>
  <update id="updateByExampleSelective" parameterType="map" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    update t_dept
    <set >
      <if test="record.deptId != null" >
        dept_id = #{record.deptId,jdbcType=INTEGER},
      </if>
      <if test="record.deptName != null" >
        dept_name = #{record.deptName,jdbcType=VARCHAR},
      </if>
    </set>
    <if test="_parameter != null" >
      <include refid="Update_By_Example_Where_Clause" />
    </if>
  </update>
  <update id="updateByExample" parameterType="map" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    update t_dept
    set dept_id = #{record.deptId,jdbcType=INTEGER},
      dept_name = #{record.deptName,jdbcType=VARCHAR}
    <if test="_parameter != null" >
      <include refid="Update_By_Example_Where_Clause" />
    </if>
  </update>
  <update id="updateByPrimaryKeySelective" parameterType="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    update t_dept
    <set >
      <if test="deptName != null" >
        dept_name = #{deptName,jdbcType=VARCHAR},
      </if>
    </set>
    where dept_id = #{deptId,jdbcType=INTEGER}
  </update>
  <update id="updateByPrimaryKey" parameterType="org.rain.mybatis.pojo.Dept" >
    <!--
      WARNING - @mbggenerated
      This element is automatically generated by MyBatis Generator, do not modify.
      This element was generated on Thu Jul 06 11:01:56 CST 2023.
    -->
    update t_dept
    set dept_name = #{deptName,jdbcType=VARCHAR}
    where dept_id = #{deptId,jdbcType=INTEGER}
  </update>
</mapper>

11.7、测试示例

11.7.1、引入相关配置文件

11.7.1.1、jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/ssm?characterEncoding=utf-8
jdbc.username=root
jdbc.password=root

11.7.1.2、mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <properties resource="jdbc.properties"/>

    <settings>
        <!--将下划线映射为驼峰-->
        <setting name="mapUnderscoreToCamelCase" value="true"/>
        <!--开启延迟加载-->
        <!--<setting name="lazyLoadingEnabled" value="true"/>-->
        <!--开启二级缓存-->
        <setting name="cacheEnabled" value="true"/>
    </settings>

    <typeAliases>
        <package name="org.rain.mybatis.pojo"/>
    </typeAliases>

    <environments default="development">

        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <package name="org.rain.mybatis.mapper"/>
    </mappers>

</configuration>

11.7.1.3、log4j.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
    <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
        <param name="Encoding" value="UTF-8" />
        <layout class="org.apache.log4j.PatternLayout">
            <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m (%F:%L) \n" />
        </layout>
    </appender>
    <logger name="java.sql">
        <level value="debug" />
    </logger>
    <logger name="org.apache.ibatis">
        <level value="info" />
    </logger>
    <root>
        <level value="debug" />
        <appender-ref ref="STDOUT" />
    </root>
</log4j:configuration>

11.7.2、创建获取SqlSession工具类

package org.rain.mybatis.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionUtils {
    public static SqlSession getSqlSession(){
        SqlSession sqlSession = null;

        try {
            //读取MyBatis核心配置文件的输入流
            InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
            //创建SqlSessionFactoryBuilder对象
            SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
            //通过核心配置文件所对应的字节输入流创建工厂类SqlSessionFactory，用于生产SqlSession对象
            SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(is);
            //创建自动提交事务的SqlSession对象
            sqlSession = sqlSessionFactory.openSession(true);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return sqlSession;
    }
}

11.7.3、创建测试类

11.7.4、根据主键查询一条数据

注意：生成的实体类没有tostring方法，因此需要手动在实体类添加tostring方法才有相关输出

    @Test
    public void testMbg(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        //根据主键查询一条数据
        Emp emp = empMapper.selectByPrimaryKey(1);
        System.out.println(emp);

    }

11.7.5、查询所有数据

注意：无条件查询（即xxxExample为null）就是查询所有

    @Test
    public void testMbg(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        //查询所有数据
        List<Emp> emps = empMapper.selectByExample(null);
        for (Emp emp : emps) {
            System.out.println(emp);
        }

    }

11.7.6、多条件查询(QBC风格)

    @Test
    public void testMbg(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        //多条件查询，QBC（query by condition）风格
        EmpExample empExample = new EmpExample();
        empExample.createCriteria().andEmpNameEqualTo("小红").andEmpIdBetween(8,10);
        empExample.or().andAgeEqualTo(20);
        List<Emp> emps = empMapper.selectByExample(empExample);
        for (Emp emp : emps) {
            System.out.println(emp);
        }

    }

11.7.7、普通修改

++++++++++++++++++++++++分割线++++++++++++++++++++++++

++++++++++++++++++++++++分割线++++++++++++++++++++++++

注意：如图所示，普通修改会将显式设置为null或未设置的字段都修改为null

    @Test
    public void testMbg(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        Emp emp = new Emp();
        emp.setEmpId(4);
        emp.setEmpName("小军");
        emp.setAge(null);
        emp.setGender("女");
        empMapper.updateByPrimaryKey(emp);
    }

11.7.8、选择性修改

++++++++++++++++++++++++分割线++++++++++++++++++++++++

++++++++++++++++++++++++分割线++++++++++++++++++++++++

注意：如图所示，选择性修改不会将显式设置为null或未设置的字段修改为null

    @Test
    public void testMbg(){
        SqlSession sqlSession = SqlSessionUtils.getSqlSession();
        EmpMapper empMapper = sqlSession.getMapper(EmpMapper.class);

        Emp emp = new Emp();
        emp.setEmpId(3);
        emp.setEmpName("小军");
        emp.setAge(null);
        emp.setGender("女");
        empMapper.updateByPrimaryKeySelective(emp);
    }